7-[Sulfomethyl)phenyl]acetamidocephalosporin derivatives

ABSTRACT

Novel cephalosporin compounds of the following formula are useful as antibiotic agents:   &lt;IMAGE&gt;

FIELD OF INVENTION

This invention relates to novel cephalosporin derivatives useful as antibiotics and processes for their preparation.

SUMMARY OF INVENTION

Compounds of the following general Formula I are used as antibiotic agents: ##STR2## wherein Y is hydrogen, chlorine, bromine, a straight or branched lower alkyl group of from 1 to 4 carbon atoms, or an alkoxy group of from 1 to 4 carbon atoms; Z is a bond, oxygen, or sulfur; W is hydrogen, methyl, amino, hydroxy, SO₃ H, or COOR₄ wherein R₄ is hydrogen or 5-indanyl with the proviso that when Z is oxygen or sulfur, W is other than hydroxy; R₁ is hydrogen or methoxy; R₂ is hydrogen, acetoxy, 1,3,4-thiadiazol-2-ylthio, 5-methyl-1,3,4-thiadiazol-2-ylthio, tetrazol-5-ylthio, 1-methyltetrazol-5-ylthio, 1,3,4-oxadiazol-2-ylthio, 5-methyl-1,3,4-oxadiazol-2-ylthio, 1,3,4-triazol-2-ylthio, 5-methyl-1,3,4-triazol-2-ylthio, 1,2,3-triazol-5-ylthio, pyridinium, or 4-aminocarbonylpyridinium, R₃ is hydrogen, a negative charge when R₂ is pyridinium or 4-aminocarbonylpyridinium, a cation of an alkali metal or an alkaline earth metal, ammonium or organic ammonium cations, a straight or branched lower alkyl group of from 1 to 4 carbon atoms, a straight or branched alkanoyloxymethyl group in which the alkanoyl moiety has from 2 to 5 carbon atoms and is straight or branched, an alkanoylaminomethyl group in which the alkanoyl moiety is straight or branched and has from 2 to 5 carbon atoms and the amine nitrogen may be substituted with a straight or branched lower alkyl group having 1 to 4 carbon atoms; an alkoxycarbonylaminomethyl group in which the alkoxy moiety is straight or branched and has from 1 to 4 carbon atoms and the amine nitrogen may be substituted with a straight or branched lower alkyl group of from 1 to 4 carbon atoms, a p-(alkanoyloxy)benzyl group in which the alkanoyl moiety is straight or branched and has from 2 to 5 carbon atoms, an aminoalkanoyloxymethyl group in which the alkanoyl moiety has from 2 to 15 carbon atoms and the amino nitrogen may be mono- or di-substituted with a straight or branched lower alkyl group having from 1 to 4 carbon atoms; and pharmaceutically acceptable salts and individual optical isomers thereof.

The non-toxic acid addition salts of the compounds such as mineral acid addition salts, for example, hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfate, sulfamate and phosphate and organic acid addition salts, for example maleate, acetate, citrate, oxalate, succinate, benzoate, tartrate, fumarate, malate, mandelate and ascorbate, are also included within the scope of this invention.

DETAILED DESCRIPTION OF INVENTION

In general Formula I the substituent group as represented by R₃ in addition to being hydrogen or a cation may also be alkanoyloxymethyl as represented by the structure: ##STR3## wherein R₅ is selected from a straight or branched lower alkyl group of from 1 to 4 carbon atoms; alkanoylaminomethyl or alkoxycarbonylaminomethyl as represented by the structure: ##STR4## wherein R₆ represents a straight or branched lower alkyl group of from 1 to 4 carbon atoms or a straight or branched alkoxy group of from 1 to 4 carbon atoms, and R₇ is selected from hydrogen and a lower alkyl group of from 1 to 4 carbon atoms; p-(alkanoyloxy)benzyl as represented by the structure: ##STR5## wherein R₈ is a straight or branched lower alkyl of from 1 to 4 carbon atoms; and aminoalkanoyloxymethyl as represented by the group: ##STR6## wherein m is 0 to 5, each of R₉ and R₁₀ is selected from hydrogen or lower alkyl of from 1 to 4 carbon atoms; and each of R₁₁ and R₁₂ is selected from hydrogen or a straight or branched lower alkyl group of from 1 to 4 carbon atoms.

Illustrative examples of straight or branched lower alkyl groups of from 1 to 4 carbon atoms which Y, R₅, R₆, R₈, R₁₁ and R₁₂ may represent are methyl, ethyl, n-propyl, isopropyl, n-butyl and tert-butyl.

Examples of lower alkyl groups of from 1 to 4 carbon atoms which R₅, R₇ and R₈ may represent are methyl, ethyl, n-propyl and n-butyl.

Examples of lower alkoxy groups which Y may represent are methoxy, ethoxy, n-propoxy and n-butoxy.

As used in general Formula I the terms 1,3,4-thiadiazol-2-ylthio, 5-methyl-1,3,4-thiadiazol-2-ylthio, tetrazol-5-ylthio, 1-methyltetrazol-5-ylthio, 1,3,4-oxadiazol-2-ylthio, 5-methyl-1,3,4-oxadiazol-2-ylthio, 1,3,4-triazol-2-ylthio, 5-methyl-1,3,4-triazol-2-ylthio, 1,2,3-triazol-5-ylthio, pyridinium and 4-aminopyridinium are taken to mean the following respective groups: ##STR7##

The compounds of general Formula I are prepared by coupling 7-aminocephalosporanic acid or a derivative thereof having the Formula II ##STR8## with a derivative of Formula III or a functional derivative thereof ##STR9## wherein R₁, R₂, R₃, Y, Z and W are as described in Formula I.

Functional equivalents of the acids as represented by Formula III include the acid halides, for example, the acid chloride, acid anhydrides, including mixed anhydrides with, for example, alkylphosphoric acids, lower aliphatic monoesters of carbonic acid, or alkyl or aryl sulfonic acids. Additionally, the acid azide or an active ester or thioester, for example, with p-nitrophenol, 2,4-dinitrophenol, or thioacetic acid, may be used, or the free acid as represented by Formula III may be coupled with the 7-aminocephalosporanic acid derivative as represented by Formula II after first reacting the acid with N,N'-dimethylchloroforminium chloride or by use of a carbodiimide reagent, for example, N,N'-diisopropylcarbodiimide, N,N'-dicyclohexylcarbodiimide, or N-cyclohexyl-N'-(2-morpholinoethyl)carbodiimide.

The reaction is generally carried out in the presence of a solvent, such as ethylacetate, acetone, dioxane, acetonitrile, chloroform, ethylene chloride, tetrahydrofuran or dimethylformamide and optionally in the presence of a base such as sodium bicarbonate, triethylamine or N,N-dimethylaniline. The temperature of the reaction may vary from about -10° to 100° C., and the reaction time may vary from about 1/2 hour to 10 hours. The cephalosporin products are isolated by conventional methods.

The salt forms of Formula I wherein R₃ is a pharmaceutically acceptable cation are prepared in the manner recognized in the art and may be formed in situ or by reacting the corresponding acid with base, for example, sodium bicarbonate or triethylamine.

The compounds of general Formula II, that is, 7-aminocephalosporanic acid and 7-aminodesacetoxycephalosporanic acid and derivatives thereof are commercially available or may be obtained from Penicillin G, cephalosporin C or cephamycin C by processes known in the art. For example, compounds of Formula IV wherein R₁ is methoxy may be prepared as described by M. Sletzinger, et al., J. Am. Chem. Soc., 94, 1408 (1972). Compounds of Formula IV may be prepared as described in U.S. Pat. Nos. 3,948,904 and 4,026,887.

When the substituent group W in the above Formula III represents an amino group suitable blocking groups, for example, tert-butoxycarbonyl, or carbobenzyloxy are employed to protect the amino function. Such blocking groups are removed after the coupling reaction by methods generally known in the art, for example, as described by Lemieux, et al., in U.S. Pat. No. 3,657,232.

Compounds of Formula III and the process for their preparation constitute additional aspects of this invention. The compounds of Formula II are prepared by treatment of a compound of Formula IV ##STR10## wherein Y, Z and W are as described above and X is a halogen atom such as chlorine, bromine or iodine with a compound of Formula V

    (m).sub.n SO.sub.3                                         Formula V

wherein M is hydrogen, a cation such as sodium, potassium, ammonium or calcium and n is 1 or 2. The reaction is carried out in a suitable solvent such as water, dimethylformamide or dimethylsulfoxide. The temperature of the reaction may vary from about -10° C. to 100° C., and the reaction time may vary from about 0.5 to 10 hours. The preferred conditions for the preparation of compounds of Formula III are the use of an equimolar mixture of a compound of Formula IV and a compound of Formula V in an aqueous medium, heating the mixture to reflux for a period of from 10 minutes to one hour and removing the solvent.

The functional derivatives of compounds of Formula III wherein the --COOH group is converted into an acid halide group may be prepared by the treatment of a compound of Formula III wherein W is other than --COOH with an acyl halide-forming reagent such as thionyl chloride, sulfuryl chloride, phosphorus pentachloride, in an inert solvent such as ether, dichloromethane, chloroform at a temperature from 20° to 60° C. for a period of time of from 0.5 hour to 5 hours. The acyl halide product is obtained upon removal of the solvent and any excess of acyl halide-forming reagent when such is present in molar excess of compound of Formula III.

The preparation of a compound of Formula III wherein W is --COO indanyl may be carried out by reacting the corresponding compound of Formula III wherein W is --COOH with one mole of 5-indanol in an inert solvent such as chloroform, dichloromethane, dimethylformamide, in the presence of N,N'-dicyclohexylcarbodiimide at a pH of about 2.5 and a temperature of from 20° to 30° C. The product is isolated upon filtration of the N,N'-dicyclohexylurea formed and subsequent removal of the solvent.

The compounds of Formula III are novel and are useful as intermediates for the preparation of the pharmaceutically useful cephalosporins of Formula I.

Compounds of Formula IV are described in U.S. Pat. No. 3,919,206, and the compounds of Formula V are known in the art or readily prepared by methods known in the art.

The compounds of Formula I may also be prepared by treatment of a compound of Formula VI ##STR11## wherein Y, Z, W, R₁, R₂ and R₃ are as described above and X is a halogen atom such as chlorine, bromine or iodine with a compound of Formula V. The reaction is carried in a suitable solvent such as water, dimethylformamide, dimethylsulfoxide at a temperature that may vary from 0° C. to 50° C. for from 0.5 to 10 hours. The products are isolated by conventional methods known in the art.

The pyridinium and 4-aminocarbonyl pyridinium derivatives of compounds of Formula I may also be prepared by the treatment of a derivative of Formula I wherein Y, Z, W, R₁ and R₃ are described above and R₂ is acetoxy, with pyridine or a suitably substituted carbamoylpyridine. The cephalosporin products are isolated by conventional methods as detailed in H. Nomura, et al., J. Med. Chem., 17, 1312 (1974).

The compounds of Formula I wherein R₂ is selected from a heteroarylthiol residue may also be prepared by the reaction of a compound of Formula I wherein R₂ is acetoxy, namely Formula VII, with an appropriate heteroarylthiol of Formula VIII as schematically described below ##STR12## wherein X, Y, W, Z, R₁ and R₃ are as described above and R₁₃ --S-- is a heteroarylthio residue selected from 1,3,4-thiadiazol-2-ylthio, 5-methyl-1,3,4-thiadiazol-2-ylthio, tetrazol-5-ylthio, 1-methyltetrazol-5-ylthio, 1,3,4-oxadiazol-2-ylthio, 5-methyl-1,3,4-oxadiazol-2-ylthio, 1,3,4-triazol-2-ylthio, 5-methyl-1,3,4-triazol-2-ylthio and 1,2,3-triazol-5-ylthio. The reaction is generally carried out in the presence of a solvent. Suitable solvents include water, methanol, ethanol, dimethylformamide and dimethylsulfoxide. The reaction is carried out by mixing in a suitable solvent a compound of Formula VII with a compound of Formula VIII, in such a way that the compound of Formula VIII may be present in a non-stoichiometric excess relative to the compound of Formula VII. The reaction temperature may vary from about 25° C. to 100° C., and the reaction time may vary from about 0.5 hour to 10 hours. The reaction may be carried out in the presence of a base such as sodium carbonate, sodium bicarbonate or triethylamine. The product of the reaction is isolated by conventional methods known in the art.

The individual optical isomers of the compounds of general Formula I wherein W represents methyl, amino, hydroxy, COOH or SO₃ H are also included within the scope of this invention.

The novel compounds of this invention are useful as antibiotic agents as demonstrated by their activity against gram positive and gram negative bacteria in vitro and in vivo and fungi. The compounds of this invention are particularly useful in that they possess a longer duration of activity than many of the well known cephalosporin compounds. Illustrative examples of bacteria against which the compounds of this invention are active are Staphylococcus aureus, Salmonella schottmulleri, Klebsiella pneumoniae, Diplococcus pneumonia and Streptococcus pyogenes.

The compounds of this invention may be administered alone or in the form of pharmaceutical preparations either orally, parenterally or topically. They may be administered to warm blooded animals, that is, birds and mammals, for example felines, canines, bovines, and equines, and humans. For oral administration the compounds may be administered in the form of tablets, capsules or pills or in the form of elixirs or suspensions. For parenteral administration they are best used in the form of a sterile aqueous solution which may contain other solutes, for example, enough saline or glucose to make the solution isotonic. For topical administration the compounds may be incorporated into creams or ointments.

EXAMPLE 1

p-Sulfomethylphenylacetic Acid

To a boiling aqueous solution of sodium bisulfite (1.47 g, 0.0141 mole) is added in portions p-chloromethylphenylacetic acid (2.6 g, 0.0141 mole). The solution is further refluxed for 30 minutes and is then evaporated to dryness to give a quantitative yield of the title compound.

Nmr (dmso-d₆) ppm (δ) 3.57 (s,2) 4.50 (s,2), 7.28 (s,4).

EXAMPLE 2

p-Sulfomethylphenylacetyl Chloride

To a solution of thionyl chloride in 20 ml of anhydrous ether is added p-sulfomethylphenylacetic acid. The mixture is stirred at room temperature until gas evolution ceases. Two drops of dimethylformamide is added, and the resulting mixture is stirred at 40° C. for 2.5 hours. The title compound is obtained after filtration and evaporation of the reaction mixture. The infrared spectrum of the product shows a characteristic acid chloride absorption at 1830 cm⁻¹ whereas the starting acid shows a carbonyl absorption at 1740 cm⁻¹.

When in Example 1 an acid selected from Table I is substituted for chloromethylphenylacetic acid the respective sulfomethyl derivative of Formula III listed in Table I is obtained, which can be converted into the corresponding acid chloride when treated as described in Example 2.

                  TABLE 1                                                          ______________________________________                                          ACID DERIVATIVE     PRODUCT                                                   ______________________________________                                         2-sulfo-p-chloromethyl-                                                                           2-sulfo-p-sulfomethyl-                                      phenylacetic acid  phenylacetic acid                                           2-(p-chloromethylphenyl)-                                                                         2-(p-sulfomethylphenyl)-                                    malonic acid       malonic acid                                                p-chloromethylphenyl-                                                                             p-sulfomethylphenyl-                                        glycine            glycine                                                     p-chloromethylmadelic                                                                             p-sulfomethylmandelic                                       acid               acid                                                        p-chloromethylphenoxy-                                                                            p-sulfomethylphenoxy-                                       acetic acid        acetic acid                                                 p-chloromethylphenyl-                                                                             p-sulfomethylphenyl-                                        acetic acid        acetic acid                                                 p-chloromethylthiophen-                                                                           p-sulfomethylthiophen-                                      oxyacetic acid     oxyacetic acid                                              ______________________________________                                    

GENERAL PROCEDURE FOR THE PREPARATION OF p-SULFOMETHYLPHENYLACETAMIDOCEPHALOSPORIN DERIVATIVES

To a solution of an appropriate derivative of Formula II (1 equivalent) and sodium bicarbonate (3.5 equivalents) in water at 0°-5° C. is added a solution of the product obtained according to Example 2 in acetone. The mixture is stirred at 0°-5° C. for 30 minutes and at about 25° C. for 1 hour. The acetone is evaporated, the pH of the aqueous phase is adjusted to 4.5, and the mixture is filtered. The filtrate is then further acidified to pH 2 to give the desired product as a solid which is filtered and dried.

EXAMPLE 3 3-[(Acetyloxy)methyl]-8-oxo-7-[[[4-(sulfomethyl)phenyl]-acetyl]amino]-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid

The title compound is obtained in 39% yield when prepared according to the above general procedure from 7-aminocephalosporanic acid (a compound of Formula II) and p-sulfomethylphenylacetyl chloride (a compound of Formula III).

Nmr (dmso-d₆ +d₂ o) ppm (δ) 2.03 (s,3) 3.3-3.9 (superimposed q, 2 and s, 2), 4.6-5.2 (superimposed m, 2; s,2 and d,1), 6.6 (d,1), 6.6 (d,1), 7.4 (s,4).

When in the procedure of Example 3 an appropriate amount of a cephalosporin derivative of Formula II, listed in the following Table II is substituted for 7-aminocephalosporanic acid and is treated with an appropriate amount of an acid chloride of a compound of Formula III listed in Table I the respective 7-[[(sulfomethyl)phenyl]-acetamido]cephalosporin products listed in Table II are obtained.

                                      TABLE II                                     __________________________________________________________________________                7-AMINOCEPHALOSPORANIC-                                               ACID      ACID DERIVATIVE   PRODUCT                                          __________________________________________________________________________     p-sulfomethylphenyl-                                                                      3-[(1-methyltetrazol-5-ylthio)-                                                                 3-[[(1-methyl-1H-tetrazol-5-yl)-                   acetic acid                                                                               methyl]-7-amino-8-oxo-5-thia-1-                                                                 thio]methyl]-8-oxo-7-[[[4-(sulfo-                             azabicyclo[4.2.1[oct-2-ene-2-                                                                   methyl)phenyl[acetyl]amino]-5-                                carboxylic acid pivalyloxymethyl                                                                thia-1-azabicyclo[4.2.0]oct-2-                                ester            ene-2-carboxylic acid, (2,2-di-                                                methyl-1-oxopropoxy)methyl ester                   p-sulfomethylmandelic                                                                     3-[(2-methyl-1,3,4-thiadiazol-5-                                                                7-[[Hydroxy[4-(sulfomethyl)-                       acid       ylthio)methyl]-7-amino-8-oxo-5-                                                                 phenyl]acetyl]amino]-3-[[(5-                                  thia-1-azabicyclo[4.2.0]oct-2-                                                                  methyl-1,3,4-thiadiazol-2-yl)-                                ene-2-carboxylic acid                                                                           thio]-8-oxo-5-thia-1-                                                          azabicyclo[4.2.0]oct-2-ene-2-                                                  carboxylic acid                                    2-sulfo-p-sulfomethyl-                                                                    3-[(acetyloxy)methyl]-7-amino-                                                                  3-[(acetyloxy)methyl] -8-oxo-7-                    phenylacetic acid                                                                         8-oxo-5-thia-1-azabicyclo-                                                                      [[sulfo[4-(sulfomethyl)phenyl]-                               [4.2.0]oct-2-ene-2-carboxylic                                                                   acetyl]amino]-5-thia-1-azabi-                                 acid             cyclo[4.2.0]oct-2-ene-2-carbox-                                                ylic acid                                          p-sulfomethylphenyl-                                                                      7-amino-3-methyl-8-oxo-5-thia-1-                                                                7-[[amino[4-(sulfomethyl)phenyl]-                  glycine    azabicyclo[4.2.0]oct-2-ene-2-                                                                   acetyl]amino[-3-methyl-8-oxo-5-                               carboxylic acid  thia-1-azabicyclo[4.2.0]oct-2-                                                 ene-2-carboxylic acid                              2-(p-sulfomethyl-                                                                         3-[(1-methyltetrazol-5-ylthio)-                                                                 7-[[carboxy[4-(sulfomethyl)-                       phenyl)malonic acid                                                                       methyl]-7-amino-8-oxo-5-thia-1-                                                                 phenyl]acetyl]amino]-3-[[(1-                                  azabicyclo[4.2.0 oxt-2-ene-2-                                                                   methyl-1H-tetrazol-5-yl)thio]-                                carboxylic acid  methyl]-8-oxo-5-thia-1-azabi-                                                  cyclo[4.2.0]oct-2-ene-2-carbox-                                                ylic acid                                          p-sulfomethylphenoxy-                                                                     3-[(acetyloxy)methyl]-7-amino-8-                                                                3-[(acetyloxy)methyl]  -7-[[[4-                    acetic acid                                                                               oxo-5-thia-1-azabicyclo[4.2.0]-                                                                 (sulfomethyl)phenoxy]acetyl]-                                 oct-2-ene-3-carboxylic acid                                                                     amino]-8-oxo-5-thia-1-azabicyclo-                                              [4.2.0]oct-2-ene-2-carboxylic                                                  acid                                               __________________________________________________________________________

EXAMPLE 4 3-[[(1-Methyl-1H-tetrazol-5-yl)thio]methyl]-8-oxo-7-[[[4-(sulfomethyl)phenyl]acetyl]amino]-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid

The title compound is obtained in 23% yield when prepared according to the general procedure from 3-(1-methyltetrazolyl-5-thio)methyl-7-amino-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid (a compound of Formula II) and p-sulfomethylphenylacetyl chloride (a compound of Formula III).

Nmr (dmso-d₆ +d₂ o) ppm (δ) 3.6 (broad, s,2), 3.87 (s,2), 4.0 (s,3), 4.2 (broad s,2), 4.75 (s,2), 5.1 (d,1), 5.7 (d,1), 7.2-7.4 (m,4).

EXAMPLE 5 3-[[(5-Methyl-1,3,4-thiadiazol-2-yl)thio]methyl]-8-oxo-7-[[[4-(sulfomethyl)phenyl]acetyl]amino]-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid

The title compound is obtained in 53% yield when prepared according to the general procedure from 3-(5-methyl-1,3,4-thiadiazolyl-2-thio)methyl-7-amino-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid (a compound of Formula II) and p-sulfomethylphenylacetyl chloride (a compound of Formula III).

Nmr (dmso-d₆ +d₂ o) 2.70 (s,3) 3.4-3.8 (superimposed, s,2 and m,2), 4.75 (s,2), 5.1 (d,1), 5.7 (d,1), 7.1-7.6 (m,4). 

We claim:
 1. A compound of the formula ##STR13## wherein Y is hydrogen, chlorine, bromine, a straight or branched lower alkyl group of from 1 to 4 carbon atoms, or an alkoxy group of from 1 to 4 carbon atoms; Z is a bond, oxygen, or sulfur; W is hydrogen, methyl, amino, hydroxy, SO₃ H or COOR₄ wherein R₄ is hydrogen or 5-indanyl with the proviso that when Z is oxygen or sulfur, W is other than hydroxy; R₁ is hydrogen or methoxy; R₂ is hydrogen, acetoxy, 1,3,4-thiadiazol-2-ylthio, 5-methyl-1,3,4-thiadiazol-2-ylthio, tetrazol-5-ylthio, 1-methyltetrazol-5-ylthio, 1,3,4-oxadiazol-2-ylthio, 5-methyl-1,3,4-oxadiazol-2-ylthio, 1,3,4-triazol-2-ylthio, 5-methyl-1,3,4-triazol-2-ylthio, 1,2,3-triazol-5-ylthio, pyridinium or 4-aminocarbonylpyridinium; R₃ is hydrogen, a negative charge when R₂ is pyridinium or 4-aminocarbonylpyridinium, a cation of an alkali metal or an alkaline earth metal, ammonium or organic ammonium cations, a straight or branched lower alkyl group of from 1 to 4 carbon atoms, a straight or branched alkanoyloxymethyl group in which the alkanoyl moiety has from 2 to 5 carbon atoms and is straight or branched, an alkanoylaminomethyl group in which the alkanoyl moiety is straight or branched and has from 1 to 4 carbon atoms and the amine nitrogen may be substituted with a straight or branched lower alkyl group having 1 to 4 carbon atoms, an alkoxycarbonylaminomethyl group in which the alkoxy moiety is straight or branched and has from 1 to 4 carbon atoms and the amine nitrogen may be substituted with a straight or branched lower alkyl group of from 1 to 4 carbon atoms, a p-(alkanoyloxy)benzyl group in which the alkanoyl moiety is straight or branched and has from 1 to 4 carbon atoms, an aminoalkanoyloxymethyl group in which the alkanoyl moiety has from 2 to 15 carbon atoms and the amino nitrogen may be mono- or di-substituted with a straight or branched lower alkyl group having from 1 to 4 carbon atoms; and pharmaceutically acceptable salts and individual optical isomers thereof.
 2. A compound of claim 1 wherein W is hydrogen, amino, CO₂ H, SO₂ H.
 3. A compound of claim 2 wherein Z is a bond.
 4. A compound of claim 3 wherein Y is hydrogen.
 5. A compound of claim 4 which is 3-[(acetyloxy)-methyl]-8-oxo-7-[[[4-(sulfomethyl)phenyl]acetyl]amino]-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid or a pharmaceutically acceptable salt thereof.
 6. A compound of claim 4 which is 3-[[(1-methyl-1H-tetrazol-5-yl)thio]methyl]-8-oxo-7-[[[4-(sulfomethyl)-phenyl]acetyl]amino]-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid or a pharmaceutically acceptable salt thereof.
 7. A compound of claim 4 which is 3-[[(5-methyl-1,3,4-thiadiazol-2-yl)thio]methyl]-8-oxo-7-[[[4-(sulfomethyl)phenyl]acetyl]amino]-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid. 